{"id":416006,"date":"2025-12-04T18:37:12","date_gmt":"2025-12-04T17:37:12","guid":{"rendered":"https:\/\/climatescience.press\/?p=416006"},"modified":"2025-12-04T18:37:15","modified_gmt":"2025-12-04T17:37:15","slug":"canada-summer-daily-high-temperature-trends-1900-2023","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=416006","title":{"rendered":"Canada Summer Daily High Temperature Trends, 1900-2023"},"content":{"rendered":"\n
\"Skyline<\/figure>\n\n\n\n

<\/p>\n\n\n\n

From Roy Spencer, PhD<\/a><\/p>\n\n\n\n

December 4th, 2025 by Roy W. Spencer, Ph. D.<\/small><\/p>\n\n\n\n

SUMMARY<\/strong><\/p>\n\n\n\n

    \n
  1. Over the period 1900-2023, the average summer (JJA) daily high temperatures across the six southernmost large provinces of Canada (British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, and Quebec) show no trend.<\/li>\n\n\n\n
  2. The average of the 3 hottest days\u2019 in each month month show a slight downward trend, while the 3 coolest days\u2019 average temperature per month shows a slight upward trend.<\/li>\n\n\n\n
  3. Recent years have generally averaged as warm as was experienced in the 1920s to 1940s, with 7 of the 10 hottest summers occurring in the 1930s.<\/li>\n\n\n\n
  4. Results for the 6 provinces separately are also presented.<\/li>\n<\/ol>\n\n\n\n

    Introduction<\/strong><\/p>\n\n\n\n

    Given media reports, it is likely that most Canadians think they have been experiencing unprecedented summer warmth in the last couple of decades. But this isn\u2019t true.<\/p>\n\n\n\n

    Below I present analyses of daily high temperatures (Tmax) from all available stations in the 6 southernmost large provinces, based upon the daily Global Historical Climate Network (GHCNd) dataset. These are the 6 provinces that border the Lower 48 and contain 86% of Canada\u2019s population.<\/p>\n\n\n\n

    I simply averaged together the relevant statistics (monthly average Tmax, average of the warmest 3 days in each month, and average of the coolest 3 days in each month) from all available stations. Each station had to have at least 90% of the days in a month reporting data for that month to be included in the analysis.<\/p>\n\n\n\n

    Since stations come and go over the years, and since there are some large terrain elevation variations in western Canada, I performed an elevation correction to these Tmax metrics, in all provinces, using the departure of each year\u2019s station-average elevation from the all-year (1900-2023) station average elevation, using a lapse rate of 6.5 deg. C per km. Corrections for average changes in station-average latitude were not done, which might be necessary in the winter since there are large North-South gradients in air temperature then. Such corrections in the summer would likely be small, but I can revisit that nuance at a later time.<\/p>\n\n\n\n

    Results<\/strong><\/p>\n\n\n\n

    I\u2019ll start with the 6-province average Tmax temperature time series, along with the total number of stations available in each year. In all plots that follow, I list the linear temperature trends, but plot a 3rd order polynomial fit to the data which captures the dominant feature of relative warmth in the 1920s to 1940s and in the most recent decades, but relative coolness in the intervening decades. In all provinces the number of stations increases from 1900 to the 1970s, then decreases substantially in recent years.<\/p>\n\n\n\n

    As can be seen in the first plot (averages for all 6 major provinces), there has been no long-term linear trend in the average summertime Tmax (0.00 deg. C\/decade), a small downward trend in the 3 hottest days per month (-0.02 deg. C\/decade), and a slight warming trend in the 3 coolest days per month (+0.03 deg. C\/decade). Relative warmth around the 1930s is evident, as well as warming in recent years.<\/p>\n\n\n

    \n
    \"Graph<\/figure>\n<\/div>\n\n\n

    I have also annotated 2021, which experienced the extreme heatwave in late June in western Canada. While that pushed the hottest 3-day average Tmax metric (red curve) to the highest average temperature of any year since 1900, the 3-month (all-days) average summer Tmax temperatures was very close to other years (3rd place, behind 1961 and 1919).<\/p>\n\n\n\n

    Notably, 7 of the 10 hottest summers occurred in the 1930s.<\/p>\n\n\n\n

    Individual Provinces<\/strong><\/p>\n\n\n\n

    The results for the individual provinces follow. (oops.. I left out Manitoba.. I will add it early tomorrow morning.<\/em>) I present them without comment; my Canadian friends can peruse the results for their home province if they wish. These are presented from West to East:<\/p>\n\n\n

    \n
    \"Graph<\/figure>\n<\/div>\n\n
    \n
    \"Line<\/figure>\n<\/div>\n\n
    \n
    \"Graph<\/figure>\n<\/div>\n\n
    \n
    \"A<\/figure>\n<\/div>\n\n
    \n
    \"A<\/figure>\n<\/div>\n\n\n

    <\/p>\n","protected":false},"excerpt":{"rendered":"

    Given media reports, it is likely that most Canadians think they have been experiencing unprecedented summer warmth in the last couple of decades. But this isn\u2019t true.<\/p>\n","protected":false},"author":121246920,"featured_media":416018,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","advanced_seo_description":"Explore Canada's summer temperature trends from 1900 to 2023, revealing no long-term increase despite recent warm media narratives.","jetpack_seo_html_title":"Canada's Summer Temperature Trends: Insights from 1900-2023","jetpack_seo_noindex":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":true,"token":"eyJpbWciOiJodHRwczpcL1wvY2xpbWF0ZS1zY2llbmNlLnByZXNzXC93cC1jb250ZW50XC91cGxvYWRzXC8yMDI1XC8xMlwvMEFRTlFHd3J3dEVuX1lfRGxlR0xCN1liS01PN3FQWUpBQVhhQ2tEa2JUV2Q0d04walV1T3VCWnlhNWcwLXhPWERIRmpOb2xIV3M0NVYyMnBwYV9JQ29FRHpLVXR0aEM1ZUZsR3NKaE03ZTNLb1dlTElKX1h3aE5JMGEtMTF0US1xLTEtMTAyNHg2NzcuanBlZyIsInR4dCI6IkNhbmFkYSBTdW1tZXIgRGFpbHkgSGlnaCBUZW1wZXJhdHVyZSBUcmVuZHMsIDE5MDAtMjAyMyIsInRlbXBsYXRlIjoiaGlnaHdheSIsImZvbnQiOiIiLCJibG9nX2lkIjoxNTU4MTI0NDl9.rUDcDpiSlCoZb8VND11yGQh8FsVjpBR2Xe63_CQ4baQMQ"},"version":2},"jetpack_post_was_ever_published":false},"categories":[1],"tags":[691829352,691839993,691831963,691826011],"class_list":["post-416006","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-extreme-heatwave","tag-global-historical-climate-network-ghcnd-dataset","tag-maximum-temperatures-tmax","tag-tmax","fallback-thumbnail"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0AQNQGwrwtEn_Y_DleGLB7YbKMO7qPYJAAXaCkDkbTWd4wN0jUuOuBZya5g0-xOXDHFjNolHWs45V22ppa_ICoEDzKUtthC5eFlGsJhM7e3KoWeLIJ_XwhNI0a-11tQ-q-1.jpeg?fit=1516%2C1002&ssl=1","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-1KdM","jetpack-related-posts":[{"id":416804,"url":"https:\/\/climatescience.press\/?p=416804","url_meta":{"origin":416006,"position":0},"title":"Canada Summer Temperature Trends, 1900-2023: Part Deux","author":"uwe.roland.gross","date":"12\/10\/2025","format":false,"excerpt":"The following figure shows the daily high (Tmax) and low (Tmin) summer (June-July-August) temperature trends, 1900-2023, for the 6 provinces from which I analyzed data. The other provinces have very few stations by comparison to these six.","rel":"","context":"In \"Canada\"","block_context":{"text":"Canada","link":"https:\/\/climatescience.press\/?tag=canada"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0Canada-map-revised-Tmax-Tmin-trends-scaled-1.jpg?fit=1200%2C831&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0Canada-map-revised-Tmax-Tmin-trends-scaled-1.jpg?fit=1200%2C831&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0Canada-map-revised-Tmax-Tmin-trends-scaled-1.jpg?fit=1200%2C831&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0Canada-map-revised-Tmax-Tmin-trends-scaled-1.jpg?fit=1200%2C831&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0Canada-map-revised-Tmax-Tmin-trends-scaled-1.jpg?fit=1200%2C831&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":416380,"url":"https:\/\/climatescience.press\/?p=416380","url_meta":{"origin":416006,"position":1},"title":"Canada Summer Daily Low Temperature Trends, 1900-2023","author":"uwe.roland.gross","date":"12\/06\/2025","format":false,"excerpt":"This is the Tmin (daily minimum temperature) version of the Canada temperature trend results I posted yesterday, which were for Tmax (daily maximum temperatures). These results are quite different: whereas the high temperatures have seen essentially no warming trends across southern Canada since 1900, the nighttime temperatures have warmed in\u2026","rel":"","context":"In \"6 provinces\"","block_context":{"text":"6 provinces","link":"https:\/\/climatescience.press\/?tag=6-provinces"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0AQPLqX6NSrUpNd4NZG8zNpbW-ANDphPlOykD8Jls4SykfF2WArofRG5qc3b9qPEIuplFfpbq-6YKP_lVKnLyi0z-hywO1Y3eceMSxDFK43hgBz6pqdiZKXWc9EHTh01j.jpeg?fit=1149%2C939&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0AQPLqX6NSrUpNd4NZG8zNpbW-ANDphPlOykD8Jls4SykfF2WArofRG5qc3b9qPEIuplFfpbq-6YKP_lVKnLyi0z-hywO1Y3eceMSxDFK43hgBz6pqdiZKXWc9EHTh01j.jpeg?fit=1149%2C939&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0AQPLqX6NSrUpNd4NZG8zNpbW-ANDphPlOykD8Jls4SykfF2WArofRG5qc3b9qPEIuplFfpbq-6YKP_lVKnLyi0z-hywO1Y3eceMSxDFK43hgBz6pqdiZKXWc9EHTh01j.jpeg?fit=1149%2C939&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0AQPLqX6NSrUpNd4NZG8zNpbW-ANDphPlOykD8Jls4SykfF2WArofRG5qc3b9qPEIuplFfpbq-6YKP_lVKnLyi0z-hywO1Y3eceMSxDFK43hgBz6pqdiZKXWc9EHTh01j.jpeg?fit=1149%2C939&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/12\/0AQPLqX6NSrUpNd4NZG8zNpbW-ANDphPlOykD8Jls4SykfF2WArofRG5qc3b9qPEIuplFfpbq-6YKP_lVKnLyi0z-hywO1Y3eceMSxDFK43hgBz6pqdiZKXWc9EHTh01j.jpeg?fit=1149%2C939&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":255147,"url":"https:\/\/climatescience.press\/?p=255147","url_meta":{"origin":416006,"position":2},"title":"Urbanization Effects on GHCN Temperature Trends, Part IV: UHI Effects on Tmax and Tmin","author":"uwe.roland.gross","date":"04\/28\/2023","format":false,"excerpt":"This is part 4 of my series on quantifying Urban Heat Island (UHI) effects on surface air temperatures as reported in the monthly GHCN datasets produced by NOAA.","rel":"","context":"In \"GHCN temperature trends\"","block_context":{"text":"GHCN temperature trends","link":"https:\/\/climatescience.press\/?tag=ghcn-temperature-trends"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":283619,"url":"https:\/\/climatescience.press\/?p=283619","url_meta":{"origin":416006,"position":3},"title":"Major Climate Alarmist Fail: \u201cThe Hottest Summer Ever\u201d that Never Was","author":"uwe.roland.gross","date":"10\/17\/2023","format":false,"excerpt":"The \u201chottest summer ever\u201d is a failure by climate alarmist and the climate boogeyman media. Use your mind and don\u00b4t follow the climate propaganda. From Watts Up With That? Guest essay by Larry Hamlin A recent WUWT\u00a0article\u00a0addresses the failure by climate alarmist media and scientists to utilize NOAA\u2019s July through\u2026","rel":"","context":"In \"climate alarmist\"","block_context":{"text":"climate alarmist","link":"https:\/\/climatescience.press\/?tag=climate-alarmist"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/image-433.png?fit=1024%2C1024&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/image-433.png?fit=1024%2C1024&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/image-433.png?fit=1024%2C1024&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/image-433.png?fit=1024%2C1024&ssl=1&resize=700%2C400 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